The present invention relates generally to motion control mechanisms and more particularly to such motion control mechanisms as are designed to provide respective periods of dwell, acceleration and constant velocity.
The use of gears and shafts to transmit rotational forces which may thereafter be converted to linear motion is well known, the same being employed in various arrangements of work transfer machinery. In certain applications this linear motion is reciprocal in nature employing a reversible electric motor or transmission to effect movement in opposite directions. Accordingly, mechanisms must be provided to shut off or disconnect the driving means from the member being moved so as to properly position same within a machine preparatory to an operation being performed on a workpiece. As any such movement cannot be stopped instantaneously, it is necessary to provide a deceleration period as well as being desirable to also provide a dwell period during which rotation of an input shaft will produce no rotation of an output shaft so as to enable maximum transfer speed and insure accuracy of positioning.
Accordingly, the present invention provides a mechanical motion control mechanism which provides a dwell period, acceleration period, constant velocity period, deceleration period and dwell period the relative lengths of which may be varied by alteration of the shape of the cam surface. In one form, the present invention employs a first gear, sprocket or wheel secured to a rotating input shaft which meshingly engages or is otherwise drivingly coupled to a second gear, sprocket or wheel supported on one end of a pivot arm the other end of which is connected to the output shaft. Cam followers are secured to the second gear and engage a stationary cam surface so as to control rotational and curvilinear movement of the second gear. In another embodiment a rack or the like is provided which is drivingly coupled to a gear, sprocket or wheel associated with output means upon which suitable cam followers are secured which cam followers engage a cam surface so as to control rotational and linear motion of the output means thereby providing controlled periods of dwell, acceleration, constant velocity, deceleration and dwell. Thus, the present invention provides a mechanical mechanism having a minimum number of moving parts which is capable of transmitting high torques thereby being operative to move massive articles which also provides a dwell period of sufficient duration to allow the drive means to be stopped without encountering overtravel. The present invention therefore greatly facilitates the transfer and positioning of articles such as workpieces within a machine.
Additional advantages and features of the present invention will become apparent from the subsequent description and the appended claims taken in conjunction with the accompanying drawings.